Body depth at pelvic fin base contained 2.7 to 2.9 times in standard length. Upper and lower head profiles slope gradually, producinq a characteristic long snout. Teeth fused to form dental plates in upper and lower jaws; upper jaw encloses lower with mouth closed; dental plates smooth, the individual teeth only visible at margins; dental plates narrow, 1.5 to 2.0 times in orbit diameter, lips covering nearly all of dental plates; upper dental plate with 1 or 2 canines posteriorly; 4 (occasionally 3) median predorsal scales; 3 rows of cheek scales (4 in Western Indian Ocean specimens), the dorsal row with 7 to 10 scales, the 2nd row with 6 to 10 scales, 3rd row with 2 to 8 scales, 4th row (if present) with 2 to 9 scales; cheek scales small, in a subtriangular patch. Pectoral fins with 13 (occasionally 12 or 14) branched rays; caudal fin emarginate in small specimens, becoming markedly so in large specimens, the lobes often greatly produced in the terminal phase.
Colour: 2 adult colour phases; initial phase - light tan, the edges of the scales paler, shading to whitish ventrally; dorsal edge of eye blue; dorsal and anal fins pale yellowish with light blue or blue-green borders (some specimens with a blue longitudinal band in middle of fins); caudal fin pale yellowish, the rays prominently streaked with light blue; pectoral fins pale with yellowish rays, the second ray pale orange, edged basally with light blue; pelvic fins light orangish with a pale blue leading edge; dental plates white in both phases;
terminal phase - body green, the scales edged in pale orange except on sides of abdomen and thorax which are solid green; a row of blue spots on abdomen on scale row below pectoral fin base, with a few blue spots below this in region of anal fin origin; thorax and abdomen pale orange midventrally; dorsal part of head green with 2 irregular pale orange-yellow bands extendin anteriorl from eye and 3 posteriorly; cheek, side of snout and ventral part of head pale orange; lips edged in orange, submarginally blue (in Indian Ocean but not Red Sea individuals, the orange of lips continues from the corner of the mouth to opercular margin, dividing the head into a dorsal green part and a ventral pale green region); dorsal and anal fins light orange-yellow with blue borders and 1 or 2 longitudinal rows of blue spots in middle of, fins; caudal fin blue with a broad band of orange in each lobe and a short longitudinal streak of orange on central part of median 7 rays; pectoral fins with upper margin blue, followed by a zone of deep yellow, rest of fin pale orangish; pelvic fins light orange with a blue lateral edge.

Maximum: 58 cm total length, 42 cm standard length, 2.3 kg; terminal phase usually larger than 30 cm standard length.

No other scarid combines such narrow dental plates (their height 1.5 to 2.0 times in orbit diameter) with small cheek scales in a subtriangular patch, and a relatively pointed snout. Furthermore all other species differ in coloration.

In coastal regions associated with coral reefs and reef flats. Colour variation has been recorded between Red Sea and Indian Ocean populations. Closely related to the Western Pacific species H. longiceps. Feeds on benthic algae.

Recorded from the Red Sea and the east African coast (south at least to Mozambique Channel) eastward to Madagascar, the Seychelles, Chagos Archipelago, Maldives and Sri Lanka.